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Waterlogged lawns

Lawns can become waterlogged if water sits on the surface and drains slowly. Waterlogging is more likely to be a problem on compacted and clay soils. However, it is worth noting that patches of dead grass where the soil proves very difficult to re-wet can be caused by a fungal problem: dry patch.

The problem

There are a number of causes that can lead to waterlogging. These include:

Waterlogging is caused when water sits on the soil surface and drains slowly, or fails to drain at all. Roots drown as the water excludes air from the soil

Poor preparation of the soil before turfing or seeding of new lawns can also lead to poor drainage and waterlogging

Waterlogging is more likely to be a problem on clay soils, or soils that are heavily compacted

There are a number of associated problems that can appear when a lawn lies wet for short to long periods:

Damp conditions encourage algae, lichens and liverworts on lawns. This includes bubble-like Nostoc algae and dog lichen. They both flourishes in badly-drained lawns but can develop wherever the aeration is poor, and may, therefore, appear on well-drained turf if the surface has become compacted and is inclined to remain damp after rain. It is also favoured by shaded conditions and poor soil fertility and so is frequently found on turf beneath trees.

Moss is a common sight where conditions are damp, but particularly if there is shade and a low pH (acid)

Clumps of rush may seed themselves, forming tussocks. See our weed control profile for more detail.

It is worth noting that patches of dead grass where the soil proves very difficult to re-wet can be caused by a fungal problem: dry patch

Control

Pricking, slitting or spiking

Pricking or slitting the surface can improve a waterlogged lawn. Shallow, 2-3cm (1in), pricking or slitting will help. However, deeper spiking is better, especially with a tool designed to leave holes 10-15cm (4-6in) deep. These holes can be filled with a free-draining material, such as proprietary lawn top dressings or horticultural sand. This allows the water to flow from the surface to deeper, less compacted layers

Hand spiking tools are available for the purpose, but an ordinary garden fork can be used. Alternatively, for larger lawns, use powered tools. Try a hollow tiner, which has hollow spikes and removes plugs of soil that are then swept up and removed

Pricking and slitting are best carried out once the excess water has drained away, especially where machinery is to be used. In small areas where standing water persists, sweep it off the lawn and into the beds before spiking with a hand spiking tool or garden fork

If your lawn is prone to waterlogging, spike it every few years in autumn. This will prevent the need for emergency action after wet winters

Keep lawns healthy

Applying fertiliser in spring will help the grass to recover from winter damage and to grow more extensive root systems that are better able to withstand drought and flooding

Wet soils and dead patches allow mosses to thrive in the lawn over winter. Remove these with a proprietary moss killer to allow the lawn to thrive

Drainage

Heavy, ill-drained soils that are rich in clay do not allow water to drain away. Where there is somewhere for water to go (a ditch, drain or soakaway, for example), drainage systems can be installed. More often there is no easy way to shed excess water. In these cases, it is sometimes worth replacing the lawn with a new one, using turf laid on a 5cm (2in) bed of sharp sand, overlaid with topsoil improved by generous manuring and thorough cultivation